$\left(-8x - 6\right)\left(-7x - 6\right) = \ ?$
Answer: $= -8x \cdot \left(-7x - 6\right) - 6 \cdot \left(-7x - 6\right)$ $= \left( -8x \cdot -7x \right) + \left( -8x \cdot -6 \right) + \left( -6 \cdot -7x \right) + \left( -6 \cdot -6 \right)$ $= 56x^2 + \left( -8x \cdot -6 \right) + \left( -6 \cdot -7x \right) + \left( -6 \cdot -6 \right)$ $= 56x^2 + \left( 48x + 42x \right) + \left( -6 \cdot -6 \right)$ $= 56x^2 + 90x + \left( -6 \cdot -6 \right)$ $= 56x^2 + 90x + 36$